Fiber-reinforced polymer (FRP) composites have been widely used to strengthen the deteriorated reinforced concrete structures due to their outstanding characteristics of light weight, high strength, as well as noncorrosion. A successful strengthening with the FRP composites would equip the existing structures with the prominent improvement in terms of the durability, ductility, and bearing capacity. Current studies indicate that a simple and reliable anchorage system for the FRP composites will help improve the performance of the strengthened structures both efficiently and economically. Up till now, various anchorage systems have been developed for the FRP composites. Therefore, it is necessary to select appropriate anchorage systems according to different needs and establish relevant design specifications. In view of the aforementioned objectives, this paper systematically summarizes the anchoring mechanism of anchorage systems for two commonly used FRP products (FRP laminates and FRP bars) in different strengthened systems. Additionally, a state-of-the-art review as well as the advantages and disadvantages of each anchorage system are presented. Finally, shortcomings in the current state of knowledge and recommendations beneficial to further study are put forward.

To effectively utilize marine resources on reefs or islands and to improve the bearing capacity and serviceability of fiber-reinforced polymer (FRP) reinforced seawater coral aggregate concrete (CAC) structures in marine environments, this paper investigates the applicability of using alkali-activated materials (AAMs) as substitutes for ordinary Portland cement (OPC) in FRP reinforced CAC structures. Three types of FRP bars, i.e., carbon-FRP (CFRP), glass-FRP (GFRP), and basalt-FRP (BFRP) bars, with different bond lengths (L = 50, 70, and 100 mm) were selected to determine the bond characteristics of FRP bars in alkali-activated seawater coral aggregate concrete (AACAC), as well as in cement-based CAC, which was chosen as the reference. Moreover, a scanning electron microscope (SEM) was employed to detect the microstructure characteristic at the interfacial transition zone (ITZ) between the coral aggregates and the paste matrix. The results indicated that the AACAC specimens contained a stronger mechanical bite force at the paste–aggregate interface and exhibited a higher splitting tensile strength (approximately 6.7% improvement) than those of the CAC specimens. Additionally, the ultimate bond strength and the initial slope of the bond–slip curves at the ascending branch (i.e., initial bond stiffness) were significantly improved by utilizing AAMs. Improvements of approximately 26.6%, 26.8%, and 16.9% were achieved in the bond strength for the specimens with CFRP, GFRP, and BFRP bars, respectively. It was concluded that the utilization of AAMs as alternatives for OPC was an effective method in improving the mechanical interaction at the paste–aggregate interface and promoting the anchorage capacity of FRP bars in CAC, which may represent a promising approach for applying AAMs in FRP reinforced CAC structures or members.

A new type of large-diameter iron-based shape memory alloy (Fe-SMA) stranded wire was developed, and its stress recovery behaviour was experimentally investigated in this study. The produced Fe-SMA stranded wires had a diameter of 15.2 mm, which were the same as the most commonly used steel-stranded wires. This kind of large-diameter Fe-SMA stranded wire matched the existing prestressed anchorage system to reduce application cost and accelerate the field application of the Fe-SMA in civil engineering. The effects of prestrain levels (4%, 6%, 8%, 10%), activation temperatures (200°C, 300°C, 400°C, 500°C), and secondary activation effect on the recovery stress of Fe-SMA stranded wires were analysed. Test results showed that the recovery stresses of the Fe-SMA stranded wire were 223–357 MPa. The maximum recovery stress was measured for the specimen with a prestrain of 8% and an activation temperature of 500°C. With increasing activation temperature, the recovery stress increased, but the increment decreased gradually. An increased prestrain level resulted in a first increase and a second decrease in the recovery stress, which was highest at the 8% prestrain level. If the shape memory effect (SME) was not fully used during the first activation, then the remaining martensitic phase changed on the second activation. The recovery stress generated by the first activation was essentially the same as those generated by the second activation at the same activation temperature. Taking the Nanshao River concrete box girder bridge in China as an example, the effect of using Fe-SMA stranded wires to compensate the prestressing loss was calculated. The results showed that the Fe-SMA stranded wire developed was able to compensate the vertical prestress loss of the prestressed box girder bridge web well and maintain the main tensile stresses at a low level during the service life of the bridge.